The present invention relates to material handling devices for the apparel industry, and more particularly to a system for mechanically separating and moving the upper ply from a stack of fabric plies.
In the manufacture of clothing it is conventional to lay out fabric in a plurality of layers on a cutting table and then cut out a desired pattern through the entire thickness of cloth layers to form a stack of apparel pieces. Individual pieces of fabric must then be separated from the stack and joined to other components of a garment in the sewing operation. Such fabric parts may include such items as pockets, sleeves, or other garment parts as are required. It is very difficult to mechanically separate a single fabric ply from a stack of identical fabric pieces. Such difficulties arise because fabric is generally not sufficiently stiff, but relatively supple and flexible. Therefore, techniques that operate satisfactorily in connection with sheets of wood, paper, or other articles that are relatively stiff are not generally successfully utilized in connection with fabric plies. Some attempts to mechanize the separation of one fabric ply from a stack of similarly shaped fabric plies include pins, pincers, suction devices, rollers, hooks, barbs, air blasts, frictional buckling devices, and the like.
As an example, one type of fabric ply separating device which utilizes an air blast is illustrated and described in the patent to Carroll U.S. Pat. No. 3,877,695. In the device a stream of air is directed from a single nozzle beneath a curved plate creating an aerodynamic lift tending to separate the upper piece of the fabric from the remaining pieces therebelow and create a rippled configuration in the fabric. A coil spring type gripper is then compressed to pinch the fabric ripples of the upper ply between the coils thereof so that the upper ply may be lifted and removed to a designated receiving area.
Other devices, such as those illustrated in the U.S. patent to Gieson et al U.S. Pat. No. 4,462,585, utilize a mechanical gripping device which indirectly and mechanically senses the distance between the jaws thereof to determine whether one or more sheets have been clamped. The mechanical linkage between the jaws and the measuring device must be precisely set and maintained so that accurate sensing occurs.
In the sequential separation, removal, and transfer of one ply at a time from a stack of fabric plies, several problems must be confronted. First of all, it is necessary to reliably lift and present one and only one ply at a time to a transfer device. Such fabrics as denim are quite heavy and therefore substantial design considerations must be given to providing sufficient air to lift one and only one ply of fabric. Secondly, in contemporary apparel manufacturing processes, it is extremely important that unnecessary steps in the operations be eliminated so that each cycle of operation occurs as quickly as possible. Thus, it is desired to eliminate lost motions such as occur in lifting and lowering prior to and subsequent to the traversing step. Finally, there must be some type of reliable test device for confirming that one and only one fabric ply has been gripped prior to the transfer of such ply to the conveyor mechanism.
Toward this end an extremely simple, reliable, and efficient separation and transfer device has been developed. Stacks of fabric plies are sequentially positioned by a carousel-type feeding apparatus in an unloading position. The uppermost ply in a stack, so positioned, is individually and sequentially separated from the remainder of the stack, and a leading edge thereof presented between the jaws of a gripping device. Once the gripping device is satisfied that one and only one fabric ply is in place between the jaws, the single ply is transferred over onto a waiting conveyor for further processing. The gripping device is so constructed that the jaws thereof open to for an obtuse angle so that the gripping device may be returned quickly to the gripping position without interferring with the free fall of the fabric ply released.
A primary feature of the present invention is the use of an aerodynamic lift means which generates lifting air currents across a substantial portion of the entire width of the upper surface of the uppermost fabric. Further, the gripping means includes an electronic test circuit mounted in one of the jaws thereof which senses the distance between the movable jaw and the stationary jaw responsive to fluctuations in a magnetic field, the magnetic field fluctuations being indicative of the number of plies being held between the two clamping jaws.
The aerodynamic lift mechanism and the gripping device which includes the test circuit therein are unique in and of themselves, in addition to the manner in which they cooperate with each other and with the remainder of the overall apparatus. Further, the carousel apparatus is unique in the manner in which a plurality of stacks of fabric plies are fed to an unloading station and sequentially lifted a distance equal to a single ply so that the uppermost unloaded ply of the stack is always at the same elevation for reliable presentation to the aerodynamic lift mechanism.
Referring now to the various components of the invention, the rotatable carousel member includes, in general, a planar member having a plurality of spaced openings therethrough arranged in a circular path thereon. The fabric bins are so mounted on the aforesaid planar member that each bin overlies one of the openings. Each bin further includes a vertically reciprocal base plate and stationary upstanding side support elements extending upwardly therefrom for storing a stack of fabric plies therein. An elevator or elevator means in the form of a linear actuator is vertically mounted on the base frame of the apparatus at the unloading position in registration with an opening in the planar member which has been moved into registration therewith. The linear actuator is movable between a first position in which the free end thereof is at a level beneath the base frame and a plurality of lifting positions in which the free end of the linear actuator engages and sequentially lifts the base plate of the fabric bins higher and higher as fabric plies are moved from the stack thereabove.
The aerodynamic lift means includes an air foil having a horizontally extending, planar rear portion and an upwardly inclined or curved front portion, the aforesaid plate having a width substantially coextensive with the major portion of the width of the fabric plies. An elongated air manifold housing having an upper surface, a lower surface, and a front wall is attached to the undersurface of the rear planar portion of the aforesaid air foil. The manifold housing has an open top trough in the upper surface thereof that extends along the major portion of the length and a plurality of spaced, horizontal passageways or a slot extending from the aforesaid trough forwardly through the front wall. The rear planar portion of the air foil is sealed against the upper surface of the manifold housing to cover the trough and pressurized air is applied to the trough. So formed, a thin sheet of air is then directed between the upper surface of the fabric ply and the air foil toward the front edge of the fabric ply. The air tends to follow the inclined forward portion of the air foil and aerodynamically lift the leading edge of the upper ply from the remainder of the stack from whence it is presented to the gripping device.
The gripping device, according to the present invention, includes a stationary support block having a planar base that forms a first stationary clamping jaw and a second clamping jaw that is pivotally linked to the support block and to a linear actuator mounted within the support block for moving the lower jaw back and forth between the clamping position adjacent the stationary upper jaw and a receiving position in which the lower jaw is arcuately withdrawn through an arc of substantially 120.degree. for purposes to be hereinafter described. A proximity switch mounted in the support block adjacent the planar face of the stationary clamping jaw generates a magnetic field which senses the position of the lower jaw with respect to the upper jaw, such relative position being indicative of the number of plies held between the clamping jaw.
Once a fabric ply is gripped and the proximity switch indicates that a single ply only is gripped, the gripping device holding a single ply is transferred laterally to a position overlying the receiving end of an off-bearing conveyor. The lower jaw is then pivotally moved to its wide open release position allowing the fabric ply to freely drop while the support block is rapidly moved back to its home position for receiving a new fabric ply. Because the lower jaw opens so wide there is no interference between the lower jaw and the released fabric ply during the return stroke. Should the proximity switch indicate a "fault" in which no plies or more than one ply is held between the gripping jaws, the gripping device is returned to the open position and the aerodynamic lift means is recycled to commence the separating step again.
It is therefore an object of the present invention to provide an improved apparatus for separating and lifting the uppermost fabric ply from a stack of fabric plies to sequentially remove and transfer plies one at a time to a conveying means or work station.
It is a further object of the present invention to provide an improved gripping device for holding a prescribed number of fabric plies therein to confirm that the number of plies is a prescribed number.
Another object of the present invention is to provide a device for separating one edge of the uppermost fabric from a stack of fabric plies utilizing an aerodynamic lift technique.
Another object of the present invention is to provide an apparatus of the type described in which the gripping device indicates an improper number of plies in the case of a "fault" and returns partially separated plies to their original position on the stack for reprocessing.
Yet another object of the present invention is to provide an apparatus for presenting stacks of fabric plies to a fabric separation device which sequentially removes and transfers fabric plies one at a time.